It's kind of tiresome the way you gloss over pretty much everything I've said, but I'm going to give it another try.
I wouldn't get too hung up on me using the term irrational, but I would presume there is a limit to the reproductive value of being able to look beyond these norms, and possibly also a positive reproductive benefit of not being able to look beyond them.
Well, contrary to what you're trying to say below, "not being able to look beyond" here does sound like a lacking capacity, not a different inclination. Same when you said in an earlier post "Too much critical thinking may lead to emancipation from custom - foregoing marriage, children, traditional lifeways. Too little critical thinking means we are not smart enough to understand what custom is, making us less likely to partner / have kids".
Rejecting out of hand every bit of conventional wisdom whose rationale you don't get is going to kill you through starvation long before it kills you, or makes you die childless, through being ostracized or lacking the desire to form a family. You're still treating Following Arbitrary Cultural Norms as a thing in itself and totally different from picking up opaque technological knowledge you couldn't derive yourself, when the two rest on the very same cognitive mechanisms. Unless you're omniscient, you can't have one without the other, at least to some degree. This also means that the null hypothesis is that "following cultural norms" (where you seem to restrict the term to arbitrary customs) is
not independently selected. In order to have an argument that it is, and thus for a discussion of what might be its benefits to make sense, you first need to reject the null hypothesis, namely that it is a side product of the mechanisms that allow us to make use of others' experiences without fully replicating them. You could do that by demonstrating that it rests on different cognitive mechanisms, or that it is dissociated, where some people are impaired at one but fully fluent at the other. Of course, that kind of dissociation in itself doesn't prove that Following Cultural Norms should be elevated to the status of selected trait - it could be (and likely is) the composite outcome of several other features, the learning strategy being just one.
Until you do that, your question may not be all that different from asking for the selective benefit of being able to ride a bike. Of course, there
are plethora of evolved capacities that play a smaller or larger role in enabling us to ride a bike, many of which have clear adaptive benefits and plausible selectionist explanations - but our "evolved bike-riding-capacity" isn't a thing in itself, as demonstrated among others by the fact that people without a single cyclist among their ancestors pick it up as easily as the Dutch.
I say mental make-up instead of a kind of g-intelligence factor because I'd assume there is more going on than ipso facto rationality. For someone who is emotionally invested in children, it's not just a rational choice being made, it's more of a world-view and mental/emotional predisposition to child-rearing. So I wouldn't assume those who are more likely to have kids are irrational, but I would assume that there is a positive correlation between reproductive success and following norms. Those who are more emotionally invested in the story so to speak, will be more motivated to achieve that story, than those not.
That's not to say that following norms is independently selected for, but mathematically the majority of us will always be norm followers because of the correlation between norms / reproduction.
I'm not discussing world-view, or intelligence as a linear quantitative variable, although I can see where you would get that impression. Sure that might be a part of it, but more broadly I'm interested in the evolution of the human mind as a whole.
What, for instance, causes the modern African to believe fervently in Nationalism even though their government is a parasite?
To the extent that this is true (I don't know that modern Africans believe in nationalism more fervently than residents of other continents), this actually shows malleability, rather than the opposite. Nationalism in its modern sense is an incredibly young phenomenon. Medieval warriors didn't kill for their country, they killed out of interpersonal obligations - they owed it to their landlord who again owed it to the king - in the case of knights; or because they were paid for killing in the case of mercenaries; or because their families were held hostage and would be made to suffer, or because it was their only way to raise their station in a society with a rigid class system where what you would become in life was almost entirely determined at birth. The nation state as we understand it (along with universal conscription) only emerged after the French revolution in Europe, and African nation states are much younger that that still.
What causes the sports fan to be emotionally invested in their team, even though it's an arbitrary group of players working for a business? Why are people unable to see through religion without an enormous amount of prompting and scientific research?
Because from the perspective of the individual learner who is a human with limited knowledge, not an idealized omniscient agent, religion is not categorically different from other opaque culturally transmitted knowledge. To someone who has never heard of the soil microbiome or the nitrogen cycle, plowing is every bit as magic as rain dances. That makes defaulting to accepting common wisdom a good survival strategy even
without a direct benefit to accepting cultural norms in a narrow sense.
The primary question is whether these realities are malleable and changeable, or do they point to something inherent in us across time.
Differentiating between in-groups and out-groups does not rely on cultural norms - baboons and chimpanzees do it too - even ants, for fuck's sake. In short, it is universal among social animals, as nearly as any biological trait is. Culture can shape
who is categorized as what, and the very fact that large and abstract entities such as the "nation", where 99.9% are people you've never met, can be conceptualized as the in-group shows a high degree of malleability, and gives hope that given the right circumstances, a majority of people might some day soon conceptualize of
humanity as it's in-group.
Our learning strategy may well be in a kind of sweet spot - enough faithful replication to allow the accumulation and preservation of opaque knowledge, but enough noise to prevent stasis - to allow for rapid cultural evolution within the limits posed by our cognitive biology, in a similar fashion to how DNA replication its in a sweet spot to allow biological evolution. But if you have an argument to relate this to intelligence you have yet to present it.
That puts it better than I could. Truthfully I've deliberately left 'intelligence' out of it because I think you are correct - it is much more complicated than that. Running with my own sweeping generalizations I'd say that propensity for logic is overrated. It's better to be the person who is intuitive and who naturally enjoys the act of living. Not just for reproduction, but for all things.
So on an evolutionary scale of the gene / individual, it's better to be emotive and social.
There again this funny idea that rationality is in conflict with being "emotive and social". I vaguely remember citing studies that reported a weak but significant
positive correlation between IQ and social intelligence last time you brought this up in the "
Why does IQ cluster around 100 points?" thread. You chose to ignore that point.